STUDY BACKGROUND INFORMATION AND RATIONALE
Non-alcoholic fatty liver disease (NAFLD):
With an estimated global prevalence of 25% among adults, NAFLD is now the commonest chronic liver disease; its progressive form, non-alcoholic steatohepatitis (NASH), has been estimated to affect 1.5%-6.5% of the population with associated increased risk of cirrhosis, hepatocellular carcinoma and liver-specific mortality. Considering the key association of fat accumulation within the liver, in particular diacyl glycerols, to the generation of whole body insulin resistance and development of type 2 diabetes, NAFLD has been considered a pre-diabetic state. NAFLD has been associated with excess risk of non-fatal and fatal cardiovascular events independently of established co-morbidities including type 2 diabetes, dyslipidemia and obesity. Individuals of South Asian ethnicity have significantly higher rates of NAFLD, abdominal obesity and cardiovascular disease than whites and ethnicity is a risk factor for NAFLD independent of diabetes, BMI, hypertension and hypercholesterolemia.
NAFLD problem in India:
Consistent with the global trend, the health and economic burdens of metabolic syndrome and NAFLD have risen in India. In 2011, India had 63 million individuals with type 2 diabetes and by 2030, that number is predicted to be a staggering 90 million. Insulin resistance (IR) has also been shown to be more prevalent in Indians compared with other ethnic groups and this has been correlated with NAFLD regardless of adiposity. Despite these links, there are a number of key differences between Indian NAFLD patients and those in the West: mean BMI is significantly lower in Indians and there is also a lower prevalence of hypertension, diabetes and metabolic syndrome in non-cirrhotic NAFLD patients.
Dietary influences on NAFLD:
Diet may be one of the key environmental factors that accounts for ethnic variation in susceptibility to NAFLD. However, there is currently a lack of research into specific dietary factors influencing susceptibility to NAFLD, in particular, with regards to macronutrients, and there are few evidence-based dietary interventions, beyond energy restriction to induce weight loss. Considering the effectiveness of a modest increase in protein content and a reduction in the glycaemic index (GI) in maintaining weight loss, we investigated the effects of a low GI diet on the liver and demonstrated that it did not increase liver fat content whereas an increase was seen with an isoenergetic high GI diet controlled for macronutrient content.
Diet has been found to influence the gut microbiome variably across human societies. Fibre encompassing a range of characteristics, is one of the fundamental components linking diet, the gut microbiome and fatty acid metabolism. The benefits of dietary fibre include improved glucose homeostasis and insulin sensitivity. Dietary fibres are at least partly fermented in the caecum and large intestine by the colonic microbiota resulting in some cases an increased production of short chain fatty acids (SCFAs) which regulate the balance between fatty acid synthesis, fatty acid oxidation and lipolysis in the body. The net result is a reduction in free fatty acid concentrations in plasma and a decrease in body weight. Dietary fibre overall is associated with greater gut microbiome diversity and we have recently shown that it is also associated with lower long-term weight gain.
